The invention relates to laundry additive and detergent compositions having components which are designed for time delayed release in laundering systems. More specifically, the invention is a laundry additive comprising an antifoam agent held by a carrier, wherein the carrier is soluble in laundry water and releases the antifoam agent into the laundering system, after a period of delay. The invention also contemplates the mixture of the delayed release additive of the invention and a conventional dry powdered or granular laundry detergent.
The invention developed from a need to provide a laundry detergent with an additive for controlling detergent foam or suds formation. In mechanical laundering operations it is often considered desirable to reduce the amount of detergent foam in the laundry water for several reasons. By reducing foaming and suds, the surfactant which would otherwise be suspended in the foam is returned to the laundry water where its cleaning action is most effective. Reducing the amount of foam in the laundry water also aids in rinsing the detergent from the laundered articles. Detergent is more easily and throughly removed from the laundered articles when the detergent is in solution, rather than in the form of foam. Also, controlling the amount of detergent foam reduces the possibility of foam overflowing the wash machine and flooding the adjacent laundry area.
Adding an antifoaming agent directly to the wash at the beginning of the laundry cycle would be immediately effective in suppressing the formation of detergent foam. Suppression of foam from the onset of the wash cycle is not generally viewed as a desirable condition. A person doing the wash may wrongly conclude that the lack of foam from the time of adding the detergent indicates that an insufficient amount of detergent has been added to the wash, or that the detergent lacks efficacy. It is therefore preferred to have a laundry detergent which has an initial foaming stage to indicate the detergent is working and is present in an adequate amount, but which also permits the foam to dissipate later in the wash cycle so that the above mentioned drawbacks of detergent foam can be avoided.
Detergent composition containing antifoaming agents held on carriers are known in the art. U.S. Pat. No. 4,451,387 discloses a granular detergent composition with a suds control agent held on a carrier. The suds control component comprises carrier having a gelatinized starch core with a mixture of silicone oil and hydrophobic silica adsorbed thereon. In this patent it is strongly preferred that the suds control agent be coated with a layer of wax to improve the storage characteristics of the suds control agent.
European Patent Application No. 0,206,522 discloses a particulate antifoam ingredient suitable for incorporation into a detergent powder composition. High and low temperature sensitive antifoaming agents are supported on a core comprised of gelatinized starch, sodium perborate monohydrate, zeolite cation exchanger, water soluble salts such as sodium tripolyphosphate and sodium sulphate in admixture with hydrophobic silica and/or paraffin wax, or hydrophobic silica and/or paraffin wax with gelatinized starch.
Attempts were made by the inventor to prepare antifoam laundry additives, as disclosed in U.S. Pat. No. 4,451,387 and European Patent Application No. 0,206,522 using gelatinized starch as a carrier, but without including a wax or material other than a carrier and antifoam agent. It was found that without wax the gelatinized starch carrier and antifoam combined to make a wet, sticky mass that was unsuitable for storage or practical use as intended with the invention.
A detergent composition containing an antifoaming agent which becomes active during the rinse cycle is disclosed in U.S. Pat. No. 4,637,890. The detergent composition contains a plurality of suds control prills comprising fatty acid soap, quaternary ammonium salt, and a silicone fluid suds suppressor. It is theorized in the patent that the prills dissolve in the relatively high pH (e.g. from about 9 to about 10.5 pH) wash water, but that the antifoam components of the prills do not become active until exposed to lower pH solutions, that is, the water of the rinse cycle. When the high pH wash water is removed from the wash machine, components of the prills are physically carried over with articles being laundered into the rinse water. The rinse water naturally has a lower detergent content than the wash water and consequently it has a lower pH which allows the prill components to dissociate, initiating antifoaming activity.
Japanese Patent Application No. 73,126,930 also discloses a coated laundering aid which remains intact during the high pH alkaline washing cycle but is soluble in rinse water.
A publication of The Dow Chemical Company entitled Formulating for Controlled Release with Methocel Cellulose Ethers discloses the use of modified cellulose ethers in medicine tablets to control and slow the release of a pharmacologically active agent over a period of time, in order to prevent the sudden "dumping" of a medication into a patient's system.